“I wrote it on a sheet of paper and handed it over to her with a big smile on my face,” he said. “She immediately had the kind of ‘initially disgusted but then laughing her ass off’ reaction I was going for.”

It seemed an efficient way for the runner and triathlete to get a date. “I have a job that occupies a lot of my time,” he said. “Having a ridiculous hour commute each way, and then also being dedicated to my gym and dedicated to my sports, I don’t have a ton of spare time on my hands.”

Bergstrom’s relationship with a fellow athlete had recently ended, and he appreciated her understanding of his early-morning wake-ups for training and racing. So, it made sense to him to write the message on his back, where fellow marathoners would see it, instead of on his front, where he’d primarily be targeting spectators.

“It’s basic marketing, to make sure you’re broadcasting your message to the audience that you’re wishing to capture,” he said. “If life is easy when you’re dating an athlete, why not broadcast in this sort of a venue?”

He went on to run the marathon—his sixth consecutive Chicago—in a personal best 3:47:58. Over the next hours and days, he received 12 Facebook friend requests from women who saw him on the course. Not all of them had run the race.

“When you run a marathon shirtless, you get a couple of people with the catcalls,” he said. “So I would kind of turn my back one way or the other if I saw a group that was particularly worth broadcasting to.”

So far, the results have been promising. Bergstrom said he’s had a few decent conversations on Facebook Messenger. Last Friday, he met up with one woman who reached out to him. She’s a marathoner who was spectating with a sign that had a photo of her cat and the message, “MY MOM IS LOOKING FOR A #CATDAD.”

“I said, ‘You know, with me showing up at the marathon with my sign on my back and you showing up at the marathon with that sign, we are missing out on a golden opportunity for future storytelling here if we don’t meet up and have a drink,’” Bergstrom said. “And we did, and it was great.”

While he’d prefer not to have to do the back-as-billboard personal ad too many more times, Bergstrom knows what he’d do differently in the future: He’d order a custom temporary tattoo instead of using a Sharpie.

“Whatever is not written backwards on my sheets from me laying on them the night before the race is now semi-permanently imprinted into the back of my bathtub,” he said. “It’s going to require a lot of scrubbing.”